> You know how applications used to be have an "Advanced" button that'd give you a nicely organized display off all the "extra" toggles?

I think your example of about:config is also an explanation for why that went away. It used to be possible to reasonably put all of the more esoteric settings on a single page (or a small, single-digit, number of pages), but that's no longer the case for many pieces of software. Also realistically the overwhelming majority of users probably already weren't going into the advanced settings, and those that were are probably more capable of handing about:config.